This invention relates in general to a closure structure for a vial whereby accidental contamination of the contents of the vial is positively prevented and, more particularly, to a closure structure for a two-compartment vial in which a lyophilized medication and a solvent can be held in complete independence from each other until it becomes desirable to use the medication.
Two-compartment vials of the kind disclosed herein have been made and have been in common use for packaging and mixing medications for many years. However, such use has been frequently and continuously interrupted by problems. For example, early two-compartment vials were equipped with rubber center plugs which did not furnish moisture-proof barriers. Accordingly, the resultant seepage of the solvent into the lyophilized medication prevented the package from having the desired shelf-life. This problem was eventually overcome after considerable experimentation which resulted in the enclosed U.S. Pat. No. 3,464,414 entitled: MIXING VIAL CONSTRUCTION.
However, a further problem continued to persist and it concerned the closure structure. More specifically, it has been difficult at best to dislodge the center plug from between the compartments, by manually depressing the stopper which is partially inserted into the neck of the vial, so that the solvent could be mixed with the medication. That is, the projecting portion of the stopper tends to bulge radially outwardly when it is urged into the neck and therefore positively and vigorously opposes movement of the stopper into the neck. Thus, the harder the stopper is pushed into the vial, the more aggravated the problem becomes.
If the stopper is made from less flexible material, in order to minimize the bulging, then leakage of the solvent past the stopper readily occurs. That is, it is extremely difficult to hold close tolerances in the inside diameter of the neck of the vial and the outside diameter of the stopper, within reasonable cost limitations. By using a relatively soft rubber stopper, having an oversized diameter, it is possible to absorb large tolerances and still prevent leakage.
In existing closure structures for the same purpose, the outer free end of the stopper is often exposed to atmosphere, hence contamination, which can contaminate the needle of the syringe as it is moved through the stopper into the vial to withdraw the mixed materials therein. That is, the syringe must pass through the surface of the stopper which has been manually engaged by the hand of the user.
Finally, existing closure structures of this type are usually in two pieces, one comprising a removable stopper cap and the other comprising a ferrule which prevents accidental removal of the stopper from the vial. Usually, these two parts are made from dissimilar materials and assembled in two steps.
Accordingly, a primary object of this invention is the provision of a closure structure including a relatively soft and resiliently flexible stopper and a cap member having a fastening portion mounted upon the neck of a vial and an integral reduced portion closely surrounding the part of the stopper extending out of the neck of the vial, said reduced portion being movable with the stopper relative to the fastening portion and the neck of the vial.
A further object of this invention is the provision of a closure structure, as aforesaid, wherein the fastening portion is positively prevented from accidentally dislodging itself from the neck of the container.
A further object of this invention is the provision of a closure structure, as aforesaid, requiring a minimum of force applied to said cap member to displace the center plug.